The present invention relates to apparatus for adjusting a hair spring in which an appropriate length of the hair spring provided as part of an oscillating element is detected by electronic circuitry and in which the rest of the hair spring is automatically cut away.
One known type of apparatus for adjusting the frequency of, e.g., a balance wheel and for cutting a hair spring thereof, is described below. The oscillation output of the balance wheel is taken out, and the frequency is multiplied to drive a motor. On the other hand, an output frequency from a crystal oscillator is divided to a predetermined frequency, applied to drive another motor. Both the motors cause differential gears to rotate. The hair spring is conveyed in accordance with the rotation of a disc which is fixed to a shaft of the differential gears. When the numbers of revolutions of the motors coincide, an operator confirms the stop of the disc, and a switch of a cutting device is actuated by the operator to cut the hair spring. However, the apparatus is disadvantageous in that the operator need always confirm the stop of the disc. Besides, the mechanical structure occupies a large part of the apparatus and the two motors are included, so that the whole construction of the apparatus is large-sized.